The present invention relates to utility networks and, more particularly, to a system and method of operating a utility network management system for network-based registration of devices associated with the delivery of commodities provided by utilities, and address resolution for such devices.
The American National Standards Institute (ANSI) has developed a series of standards and associated protocols to enable data generated by utility meters, e.g. electric meters, to be electronically communicated. Similarly, protocols have been developed for communication with Distribution Automation (DA) devices employed in the delivery of utility services. The invention disclosed herein deals with addressing, address resolution, and the infrastructure required to provide comprehensive network services that are supported by these standards.
For example, ANSI C12.19 defines the formats for meter data and structure of tables containing such data. Earlier versions of the ANSI metering protocols provided for media-dependent mechanisms to interface with meters that conform to the ANSI C12.19 standard. Two of these earlier versions are germane to an understanding of the context of the present invention:                ANSI C12.18 (or PSEM) was designed to interface meters over a serial port. It allowed for a primitive set of protocol operators (or “verbs”) that allowed programmatic interrogation (i.e., “reads”) and programming (i.e., “writes”) to meters. This interface was initially designed for handheld devices, but came to be used by a non-standardized set of communication modules for networking meters.        ANSI C12.21 extended C12.18 to provide an interface to meters via modems that communicate over telephone systems.        
A more recent standard, C12.22, came about as a way for the utility meter industry to abstract away the complexities of several disparate networking technologies. For instance, many cellular technologies such as GPRS and CDMA 1XRTT were becoming widely available, as were a few fixed networking technologies of limited scale. The C12.22 protocol was under development well before the notion of large scale, fixed networks for residential metering was commonly shared.
Regardless of any agnosticism or support at the Physical layer (L1) of the OSI network model, the C12.22 standard does maintain agnosticism at Data Link (L2) and Network (L3) layers. In order to do so, C12.22 provides, at the Application layer (L7), a scheme for addressing, address resolution, maintaining state, fragmentation/re-assembly, and application layer routing, and other features. For any of these services and applications to be useful, one must resolve lower layer networking addresses in order to forward frames using C12.22 to C12.19-compliant devices. In a flat, “point-to-point” cellular network (e.g., GPRS or CDMA1XRTT), this may be a simple process: bind an IP address to a C12.22 application layer address (i.e., a C12.22 apTitle) in a registry. And in smaller networks with built-in hierarchy (or constraints), this process is straightforward.
However, C12.22 was not designed with a view towards large-scale networked commodity metering deployments (for example AMR/AMI and in-premise networks); nor was it designed for environments where the underlying network infrastructure addresses are highly dynamic.
In the area of Distribution Automation, protocols for communication with Distribution Automation (DA) devices have been developed and employed in the delivery of utility services.
For example, the MODBUS® protocol defines a message structure that controllers recognize and use, regardless of the networks in which they communicate. MODBUS describes the process a controller, such as a Supervisory Control and Data Acquisition (SCADA) system, uses to request access to another device, such as a DA device. Moreover, MODBUS describes how the SCADA system will respond to requests from the DA device and how errors are detected.
The MODBUS protocol is used to establish master-slave communications between the SCADA system and the DA device. MODBUS has two types of serial transmission modes, ASCII and RTU. In ASCII serial transmission mode, each 8-bit byte in a message is sent as two ASCII parameters, whereas, in RTU serial transmission mode, each 8-bit byte in a message is sent as two 4-bit hexadecimal characters.
In another example, DNP 3.0 is a protocol used by a SCADA system to communicate data and control commands to a DA device. DNP 3.0 and MODBUS protocols normally operate over serial lines, but have recently been modified to also operate over TCP/IP. In the DNP 3.0 protocol, each device has a two-byte address. In the MODBUS protocol, each device has a single byte address. Both of these addresses may be associated with an IP addresses when TCP/IP is used. Typically the SCADA system communicates with small groups of these devices. The SCADA system decides which DNP 3.0 or MODBUS address it is going to send the command to, and then it looks up the IP address in a static table. However, in the case of a wide-scale network architecture where all nodes communicate with a common back-office host, the 1 or two byte addresses may not be sufficient to distinguish all the devices in a utilities' territory. Further, the DA communication node that is attached to the DA device may change its IP address when it joins different IP networks.